Does anyone know what happens to the stack pointer after making an Int 10h call from a DOS4G app? I've patched ICR2 to make a dummy interrupt during the aspect ratio calculation, but the stack pointer appears to be different to what it is in the execution trace, the other registers seem to be preserved. Some documentation on how this is handled would be useful.

I know Int10h is a real mode call. Maybe I could modify the Int10h vector to directly int10h instead of massaging a protected mode to real mode transition. I don't know if that's possible.

The reason this is important is the game appears to use different aspect ratios: 4:3 for external views and something closer to 1:1 for cockpit views . I could probably create a code cave and add my code in, but I'm not great with dos and don't really know where I can insert stuff, assuming there's unused space in there.

Maybe this could be helpful: https://www.opferman.com/Articles/Text/index. … up=1001&order=4

Makus wrote on 2025-10-23, 21:27:

Maybe this could be helpful: https://www.opferman.com/Articles/Text/index. … up=1001&order=4

Thanks @Makus!

Just a quick update on widescreen support with ICR2, the aspect ratios are correct for 16:9 and 32:9 through modelview matrix manipulation, but the sprites in game are scaled equally in both dimensions so they're out of whack at the moment:
[EDIT] https://youtu.be/broxTVRiUEI (sprite scaling fixed)[/EDIT]
https://youtu.be/jwRRvG4TJkA

(Also available here for with just a sign-in and an extra formula in the description: https://www.patreon.com/posts/indycar-racing- … ntent=join_link)

An earlier attempt is available here with indepdent x and y scaling (of models):
https://youtu.be/gSLTet0VncI
(https://www.patreon.com/posts/indycar-racing- … ntent=join_link)

The game uses a 3x3 matrix with both 16.16 and 2.30 fixed point arithmetic.

My xbox one controller (wired) seems to not be recognized in icr2. Dosbox does recognize it (Verified it by going ctrl+f1 before going into icr2), but inside the game, the joystick calibration doesn't register the movement of the joystick, neither of the triggers. The inputs sort of "glitch" when in the calibration tab. Im using the latest rendition alpha (watemarked) along icr2rend by gplaps.

josemike03 wrote on Today, 00:55:

My xbox one controller (wired) seems to not be recognized in icr2. Dosbox does recognize it (Verified it by going ctrl+f1 before going into icr2), but inside the game, the joystick calibration doesn't register the movement of the joystick, neither of the triggers. The inputs sort of "glitch" when in the calibration tab. Im using the latest rendition alpha (watemarked) along icr2rend by gplaps.

I have one a 360 pad, I'll see if I can get it to work. Give me an hour to get back to my desk.

You're right. It doesn't work in dosbox-rendition but does in dosbox-staging-rendition.

Dosbox-rendition does appear to detect it correctly, even though it doesn't actually work. Dosbox uses SDL1 and staging uses SDL2. Let me see if it's fixable or whether it needs a separate xinput codepath.

OK, it looks like I have to port SDL3's XInput support to SDL1. That's currently underway.

@josemike03, This will take quite a while, the XInput code in newer SDLs is C++ based and SDL1 is C based. I already have some XInput code I used for something else. I can try and integrate that directly into dosbox. I'll try doing that once I get widescreen working. It's a bit of a big job, but its next on my list after widescreen.